Convert Expression to Reverse Polish Notation

Given An expression string array, return the Reverse Polish notation of this expression. (Remove the parentheses)

Example

For the expression [3 - 4 + 5] (which denote by ["3", "-", "4", "+", "5"]), return [3 4 - 5 +] (which denote by ["3", "4", "-", "5", " +"])

1  Public classSolution {2     /**3 * @param expression:a string array4 * @return: The Reverse Polish notation of this expression5      */6      PublicArraylist<string>CONVERTTORPN (string[] expression) {7arraylist<string> list =NewArraylist<string>();8stack<string> stack =NewStack<string>();9 Ten          for(inti =0; i < expression.length; i++) { OneString str =Expression[i]; A             if(Isoperator (str)) { -                 if(Str.equals ("(")) { - Stack.push (str); the}Else if(Str.equals (")")) { -                      while(!stack.isempty () &&!stack.peek (). Equals ("(")) { - List.add (Stack.pop ()); -                     } + Stack.pop (); -}Else { +                      while(!stack.isempty () && order (str) <=Order (Stack.peek ())) { A List.add (Stack.pop ()); at                     } - Stack.push (str); -                 } -}Else { - List.add (str); -             } in         } -          while(!Stack.isempty ()) { to List.add (Stack.pop ()); +         } -         returnlist; the     } *  $     Privateboolean isoperator (String str) {Panax Notoginseng         if(Str.equals ("+") || Str.equals ("-") || Str.equals ("*") || Str.equals ("/") || Str.equals ("(") -|| Str.equals (")")) { the             return true; +         } A         return false; the     } +  -     Private intorder (String a) { $         if(A.equals ("*") || A.equals ("/")) { $             return 2; -}Else if(A.equals ("+") || A.equals ("-")) { -             return 1; the}Else { -             return 0;Wuyi         } the     } -}

Convert Expression to Reverse Polish Notation